1. Field of the Invention
The invention relates to a glass ceramic cooktop which comprises a glass ceramic plate having a flat upper surface and a lower surface with a knob pattern thereon, and radiant heating elements or induction heating disposed below the glass ceramic plate and leaving open partial areas around the heating.
2. Description of Related Art
From DE 196 33 706 C2, glass ceramic plates for cooktops are known, which are provided with a knob pattern on their lower surface, except for a band free of knobs. In the area of this knob-less band, the upper and lower surfaces of the glass ceramic plate exactly run in parallel to each other, so that capacitive sensors can be mounted there.
The knob pattern on the lower surface of the glass ceramic plate renders the latter less susceptible to scratches during manufacturing and in assembly. The knobs have a height ranging between 40 and 200 μm and are clearly visible from the smooth upper surface through the glass ceramic plate. This even applies if a display area is provided below the glass ceramic plate. Therefore, it is desired to have the knobs removed there. However, glass ceramic plates for cooktops are very sensitive, so that grinding off the knobs appears questionable. Namely, since the height of the knobs varies it is in fact almost impossible to grind off the knobs alone, rather it is necessary to grind a bit into the surface of the bottom side of the cooktop. This, however, creates a step in the cooktop, entailing a risk of breakage along this step, namely when subjected to a load, i.e. a load from above during use.